Some minor changes based on 6.0 development. We will no longer integrate handling of AttributeConverter, Comparator and MutabilityPlan into the "Type" itself (in fact "Type" will largely go away). Instead those things are tracked on the Navigable. In terms of annotation/xml there is not much of a difference.

So ultimately for a basic-valued Navigable we need to determine its:

1. BasicType (which will continue to exist)
   1. JavaTypeDescriptor
   2. SqlTypeDescriptor
2. Comparator
3. MutabilityPlan